Routine pulmonary function tests in young adolescents with asthma in
general practice

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Abstract
Objective: To assess the value of performing routine
pulmonary function tests by flow-loop spirometry in young
adolescents with asthma. Design: A prospective clinical study comparing
clinical assessment and patients' self- reporting of asthma
severity with the results of pulmonary function tests. Setting: General practice in a small rural community
of about 30 000 people. Patients: Young adolescents with asthma, aged 10-15
years, were enrolled in the study over a two-year period from July 1993
to June 1995 when they presented for either elective, interval
assessments or with an acute exacerbation of asthma. Main outcome measures: Discrepancy between (i) the
doctor's and the patient's perception of asthma control (six scale
measures) and the consequent management plans, and (ii) the results
of pulmonary function tests that indicated less than adequate airway
function (i.e., forced expiratory volume in one second as a
percentage of predicted vital capacity for height and sex [FEV 1 %]
less than 65% or average flow rate over the middle 50% of forced
vital capacity as a percentage of predicted normal value [FEF 25%-75%
] less than 65%). Results: Twenty-seven adolescents with asthma were
assessed on a total of 37 occasions. The results of pulmonary function
tests did not correlate with asthma symptoms and treatment in 11 of the
37 assessments (30%; 95% confidence interval [CI], 16%-47%). The 11
assessments were performed on eight patients. Conclusions: This small community-based study of
adolescents with asthma supports the view that pulmonary function
testing by flow-loop spirometry should be part of the routine
assessment of acute and chronic asthmatics. Further study in a larger
community is needed to clarify the frequency of over- and
underestimation of asthma severity in this difficult age group.
MJA 1996; 165: 469-472

Older children and adolescents often have difficulty assessing the
severity of their asthma, 1
and consequently pulmonary function tests have been recommended for
those with frequent or chronic asthma who are able to perform
spirometry adequately. 2-4
Pulmonary function testing by flow-loop spirometry allows
measurement of forced expiratory volume in one second as a percentage
of the predicted vital capacity for height and sex (FEV 1 %), and forced
mid expiratory flow (FEF 25%-75% : the average flow rate over the
middle 50% of forced vital capacity).

While peak flow monitoring and FEV 1 % have been used for decades as a
measure of pulmonary function, forced mid expiratory flow is not as
well known a measure, but is more sensitive than FEV 1 in
detecting small airways obstruction. 2 Pulmonary function tests have been
shown to be useful in adults, but there are few studies of their useful
ness in children and young adolescents with asthma. One study found
that 17% of apparently well children with asthma had a low forced
expiratory volume in one second / vital capacity ratio (FEV 1 /FVC) and
54% had low forced mid expiratory flow (FEF 25%-75% ), suggesting
that, without these tests, both patients and doctors were unable to
detect mild degrees of broncho constriction, especially of the
smaller airways. 5

To date, no study has described the use of pulmonary function tests as
part of routine community medical practice in young adolescents. In
fact, in some centres, spirometry tests are not yet done routinely in
chronic asthmatics in this age group. We performed pulmon ary
function tests in adolescents with asthma in an Australian country
setting, comparing patients' and doctors' clinical assessment of
asthma severity with the results of routinely performed pulmonary
function tests.

Methods
This two-year study took place in Colac, Victoria (population, 14
000; regional population, 30 000) between July 1993 and June 1995. All
young adolescents with asthma (recurrent wheeze responsive to
bronchodilators) between the ages of 10 and 15 years pre senting to
their general practitioner Monday to Friday either for an elective
asthma management review, or because of an acute exacerbation of
their asthma, were assessed by the general practitioner and included
in the study. No adolescents were excluded from the study or refused to
participate. Appointments for elective management reviews
(interval assessments) had been made weeks in advance. An acute
exacerbation of asthma was defined as an appreciably more severe
wheeze and cough than usual (as assessed by the general
practitioner).

The severity of symptoms and the perception of asthma control were
assessed by the general practitioner, giving day and night symptom
scores (0-5), and a wheeze description, based on questioning of the
patient. The doctor and the patient then separately graded asthma
control as excellent, very good, fair, poor, or very poor. (The
scoring system is given in the footnote to the Table).

Forced expir atory volume in one second (FEV 1 ) and forced mid
expiratory flow (FEF 25%-75% ) were measured -- on the same day if it was
a daytime presentation (usually immediately after the clinical
assessment) or the morning after if it was an evening presentation. An
Alpha Vitalograph spirometer (Fisher & Paykel, Melbourne, Vic.) was
used and the tests were conducted by the senior physiotherapist at
Colac Hospital (E A T), who had attended the spirometry technician's
course run by the Department of Respiratory Medicine, Alfred
Hospital, Melbourne. The tests were repeated if the assessment was
judged to be inadequate by the physiotherapist. The effect of
bronchodilators on pulmonary function tests was determined in all
patients, with recordings being taken 20 minutes (in one patient 25
minutes) after bronchodilator therapy.

The pulmonary function tests were done without knowledge of the
clinical status of the patient and the results were made available to
the treating doctor if requested. The patients' previous home peak
expiratory flow measurements were also recorded, as was peak flow
measured with the spirometer.

The results of the pulmonary function tests were considered not to
correlate with asthma symptoms and treatment, and to be likely to lead
to a change in asthma management, if:

During an interval
assessment:

The patient complained of no, few or only moderate
symptoms, the doctor felt asthma control was excellent, very good or
reasonable, respectively, and did not change treatment, but FEV 1 %
(normal, > >80%) or FEF 25%-75% (normal, > >65%) was less than
65%.

The patient and the doctor thought control was poor, the dose of
maintenance asthma therapy was increased, but pulmonary function
tests revealed no evidence of bronchospasm.

During assessment of an acute exacerbation:

The patient and the
doctor felt current asthma control was excellent or very good, no
increase in dose of inhaled steroids was suggested and no oral
corticosteroids were prescribed, but FEV 1 % or FEF 25%-75% was less
than 65%.

Results
Twenty-seven adolescents with asthma (male : female ratio, 2 : 1) were
assessed on a total of 37 occasions. On 22 occasions they were elective
interval assessments and 15 were for an acute asthma exacerbation.
Nineteen patients (70%) were monitoring peak flow at home.
Twenty-nine (78%) of the pulmonary function tests were within two
hours, four (11%) between two and four hours and four (11%) between
four and 14 hours after the clinical assessment. Satisfactory
spirometry measurements were achieved in all patients without
difficulty (fewer than four repeats).

Of the 22 interval assessments, 16 (73%) were in patients taking
inhaled corticosteroids (in 11 of these the patients were taking more
than 700 µg inhaled corticosteroids per day, and in five FEF
25%-75% values were less than 65%). In two (9%) interval assessments
peak expiratory flows were less than 300 L/min (in only one of the
assessments with FEF 25%-75% less than 65% were peak flows less than
300 L/min).

Of the 15 acute exacerbation assessments, eight (53%) were in
patients taking inhaled corticosteroids (in three of these the
patients were taking more than 700 µg inhaled corticosteroids
per day). In five (45%) acute exacerbation assessments peak
expiratory flows were less than 300 L/min (four were unavailable).

Details of the patients whose pulmonary function tests did not
correlate with asthma symptoms and treatment are given in the Table.
Overall, pulmonary function tests not correlating with clinical and
patient assessment of asthma severity were found in 11 of 37
assessments (30%; 95% confidence interval [CI], 16%-47%). If only
those tests performed within four hours of the clinical assessment
are included, pulmonary function tests in 10 of 33 assessments (30%;
95% CI, 15%-46%) did not correlate with asthma severity. Pulmonary
function tests in six of the 22 interval assessments (27%; 95% CI,
11%-50%) showed FEV 1 % or FEF 25%-75% to be less than 65% when
management had not been changed after clinical assessment (Cases
1-6). During acute exacerbations, four of 15 assessments (27%; 95%
CI, 8%-55%) showed FEV 1 % or FEF 25%-75% values to be less
than 65% when no change in treatment had been made on clinical grounds
(Cases 8-11). Tests in one patient (Case 7) showed normal pulmonary
function after clinical assessment had suggested poor asthma
control. Her pulmonary function tests were carried out within two
hours of the clinical evaluation; her inhaled cortico steroid dose
had been doubled.

Discussion
This community-based study of all young adolescent asthmatics
presenting to their general practitioners in a country town found
that in 30% of assessment opportunities the results of pulmonary
function tests were likely to change management. This proportion was
maintained even if slightly delayed pulmonary function tests (4-14
hours) were excluded. This result is comparable with previously
published findings that 54% of apparently well asthmatics had lower
than expected FEF 25%-75% values at follow-up, despite being
asymptomatic. 5

At interval assessments in which management had not been changed and
the results of pulmonary function tests were low, three of five
adolescents (Table: assessments 1, 3-6) reported frequent
wheeze. The other two thought their asthma was well controlled;
however, their FEF 25%-75% values were 62% and 42%, respectively. In
these patients peak flows, measured at home and by spirometry, were
all above 300 L/min and this may have accounted for ALIGN=TOP the reluctance to
change therapy. However, it has been shown previously that peak flow
results can be misleading, and widely varying optimal values can be
expected. 3 A low expectation
of what can be achieved in frequently symptomatic patients may
contribute to a less aggressive approach in adolescents with asthma.

The rather frequent use of inhaled corticosteroids in relatively
high doses in this small sample of asthmatics suggests that a more
objective measure of asthma status should be used. Potential overuse
of inhaled corticosteroids in these growing young people may not
always safeguard those at risk of more severe asthma. Six of 11
patients (55%) taking more than 700 µg inhaled
corticosteroids had FEF 25%-75% values less than 60%, suggesting
that in these patients an even higher dose of inhaled corticosteroid
may be required. More specific alterations to long term inhaled
steroid use would be possible if pulmonary function tests were
performed regularly.

During assessments for acute exacerbation the rate of pulmonary
function tests not correlating with symptoms was still high (27%) and
the FEF 25%-75% was worryingly low in three patients in whom
management was not altered (Table: assessments 8, 9, 10, and 11).
These three adolescents all had frequent wheeze, but presumably were
not distressed, with peak flows (measured at home and by spirometry)
above 320 L/min. Pulmonary function tests gave an indication of small
airways disease which they were not aware of or was not revealed by
their peak flow measurements.

Our study involved a small number of patients and the confidence
intervals calculated suggest a larger study is necessary.
Nevertheless, data on mortality in asthma indicate that
underestimation of asthma severity can be extremely important.
Robertson et al. found that about 35% of possibly preventable asthma
deaths may have been related to medical practitioner
underestimation of asthma severity. 6

The full implications of FEF 25%-75% values in the 55%-65% range is not
yet certain. A long term follow-up of asymptomatic patients with
values in this range has not yet been done. Most of our patients with low
FEF 25%-75% values not correlating with symptoms had
values below 55% (Table: 7 of 10 assessments). Thus, even if the
implications of an FEF 25%-75% value between 55% and 65% is disputed,
the frequency of the lower results suggests more aggressive
treatment is required.

This relatively small study of asthmatic adolescents in a small
country town strongly supports the view that pulmonary function
tests need to be part of the routine assessment of acute and chronic
asthmatics.